Hitherto, a syringe for applying a medicament to a limited diseased part such as that in the oral cavity has been known (see, for example, Japanese Design Publication Nos. 464190 and 681235) Such a syringe comprises a barrel fitted with a plunger and a nozzle. Usually, a barrel has a hollow cylindrical portion and a tubular portion which is thinner than the cylindrical portion and connected to one end of the cylindrical portion. The other end of the cylindrical portion is an open end and has a flange. The cylindrical portion may be slightly tapered from its open end to the tubular portion and the tubular portion is connected to the nozzle. The plunger has a gasket on one end of its piston rod to be pushed in the barrel through its open end. The outer diameter of the gasket is substantially the same as the inner diameter of the cylindrical portion. The other end of the plunger is pushed to insert the plunger into the barrel. A medicament is filled in the barrel and, when it is applied to the diseased part, the plunger is fully inserted into the barrel to push out the medicament through the nozzle toward the diseased part part. The plunger has a shoulder portion formed on a appropriate position of the side wall of the plunger and, as the plunger inserted into the barrel, the shoulder portion is brought into contact with the flange of the cylindrical portion to limit the insertion.
And, in order to fill a medicament having high viscosity into the barrel, it is filled through the open end of the barrel with a filler nozzle, while the barrel is set upright so that the open end is at the top thereof because it is difficult to suck the medicament into the barrel through the nozzle of the syringe. In this case, the filler nozzle tip is firstly located in the bottom of the barrel and then the filler nozzle is moved toward the open end, while filling of the medicament is continued with preventing inclusion of air. The medicament is filled up to tee level of the flange of the cylindrical portion. This filling manner is necessary to prevent inclusion of air between the gasket and the medicament when the plunger is pushed into the barrel.
However, in this case, since the medicament is filled up to the level of the flange of the cylindrical portion, the medicament is overflowed from the barrel when the plunger is pushed in the barrel to smear the flange and thereabout. Further, it is necessary that the plunger moves a certain distance toward the inside of the barrel to make the plunger in a self-supporting state prior to the use of the syringe for application of the medicament. In this case, a volume of the medicament corresponding to the movement of the gasket in the barrel is pushed out through the nozzle and discarded without utilizing it. This is uneconomic and, even if it can be recovered, it is very difficult to return it to the filler with maintaining an aseptic state.
Further, in the case of a dentist's syringe, the diseased part is located in the inner part of the oral cavity and therefore the barrel should have a certain length so that the nozzle reaches to the diseased part. Naturally, this rules the length of the plunger which is inserted into the barrel. That is, the plunger should also have a corresponding length. However, from the viewpoint of handling properties, it is preferred that the plunger has a relatively shorter length, and the requirement for making the plunger shorter is inconsistent with the requirement for making the barrel as long as possible. It has been requested to solve this inconsistent matter. And, even when the barrel is longer, the medicament should be also filled up to the level of the flange of the cylindrical portion to prevent inclusion of air, which makes the volume of the medicament to be filled much larger in comparison with that required for actual application. The excess amount of the medicament is discarded without utilization. This is uneconomic and, particularly, in the case that a syringe in which a medicament has been already filled is marketed, the excess amount of the medicament reflects the increase in the production cost of the syringe.